A database can be defined as an integrated collection of logically related objects that are stored in a computer system. In an XML (extensible markup language) database, objects stored in the database are represented as XML documents. Data in the XML documents may be queried, exported and serialized into a desired format.
Existing XML database products may store only a single version of each object. Later versions of the object that are stored to the database may overwrite the current version. In other words, the database may keep only the most recent version of the object. In some applications, object history is valuable and it may be desirable to have multiple versions of objects stored in a database so that users can query older versions of objects.